1. Field of the Invention
The present invention relates generally to drive systems for transmitting torque from a power source such as an engine, to mechanism which is to be driven thereby, and more particularly to a two speed axle assembly for motor vehicles having improved shiftability.
2. Description of the Prior Art
Two speed axle assemblies are frequently employed in the drive train of motor vehicles such as automobiles and trucks so as to afford the driver the option to choose between direct drive and overdrive speed ratios, or between direct drive and underdrive speed ratios as the case may be, to adapt to changing load and speed conditions. Such two speed axle assemblies commonly employ sun gears and an associated planetary gearset, with shifting means for selectively locking the planetary gearset in the direct or the overdrive/underdrive mode. The shifting means employed heretofore have permitted undesirable gear racheting during shifting from one mode to the other, and may potentially permit dangerous free wheeling during the shifting. Thus, the planetary gearset of such axle assemblies must disengage in one mode before it engages in the other thereby, in effect, uncoupling the engine from the drive train so as to lose the driving or braking effect of the engine.